The present invention relates to an improved solenoid valve for regulating the fuel supply pressure of an internal combustion engine.
In modern engine fuel supply systems, a high-pressure pump feeds the fuel to a distributor or so-called xe2x80x9ccommon railxe2x80x9d, which supplies the various engine cylinder injectors; and a solenoid valve controlled by a pressure sensor is normally provided to control and keep the fuel pressure in the distributor constant and to drain into the tank any surplus fuel supplied by the high-pressure pump. The solenoid valve comprises a supply conduit communicating with the delivery conduit of the high-pressure pump; and a shutter controlled by an electromagnet and cooperating with a seat in the supply conduit.
In one known pressure regulating solenoid valve incorporated in a radial-piston pump, the shutter is defined by a ball controlled by the end of a stem on the electromagnet armature and cooperating with a conical sealing seat at one end of the supply conduit.
On account of dirt, e.g. metal particles, settling between the ball and the conical sealing seat, the above solenoid valve is subject to sealing problems resulting in a fall in pressure and, hence, malfunctioning of the supply system as a whole. And, due to the extremely high operating pressure involved, e.g. in the region of 1400 bar, ordinary filtration means in the supply conduit likewise result in a fall in pressure along the supply conduit.
It is an object of the invention to provide a pressure regulating solenoid valve, which is extremely straightforward and reliable, and provides for eliminating the aforementioned drawbacks typically associated with known solenoid valves.
According to the present invention, there is provided a solenoid valve for regulating fuel supply pressure, and which comprises a fuel supply conduit, and a shutter controlled by an electromagnet and cooperating with a seat in said conduit, and is characterized by fuel filtration means located in said conduit and comprising a wall having a number of openings for preventing particles of dirt from infiltrating between said seat and said shutter, without producing an excessive fall in fuel pressure; the thickness of said wall being less than 1 mm; and the width of said openings being less than 0.25 mm.